Network Plus 2005 In Depth

802 Glossary

patch—A correction, improvement, or enhancement to part of a software application, often distributed at no charge by software vendors to fix a bug in their code or to add slightly more functionality.

patch cable—A relatively short section (usually between 3 and 25 feet) of cabling with connectors on both ends.

patch panel—A wall-mounted panel of data receptors into which cross-connect patch cables from the punch-down block are inserted.

pattern—In the context of installing the NetWare NOS, a choice of server type to install (for example, Basic NetWare File Server). Based on the pattern, the installation program will include files necessary for specific services or, if the Customized NetWare Server pattern is selected, prompt the user to select which services should be installed.

PBX (private branch exchange)—A telephone switch used to connect calls within a private organization.

PC Card—A PCMCIA standard that specifies a 16-bit interface running at 8 MHz for externally attached devices. PC Cards’ characteristics match those of the ISA expansion card. And like the ISA standard, the PC Card standard suffered from its lower data transfer rates, compared to other PCMCIA standards.

PCI (Peripheral Component Interconnect)—A 32 or 64-bit bus that can run at 33 or 66 MHz, introduced in its original form in the 1990s. The PCI bus is the NIC connection type used for nearly all new PCs. It’s characterized by a shorter length than ISA or EISA cards, but has a much faster data transmission capability.

PCI Express—A 64-bit bus standard capable of transferring data at up to 500 MBps in full-duplex transmission. PCI Express was introduced in 2002. It follows a new type of bus design and offers several advantages over the old PCI, and its expansion cards can fit into older PCI slots, with some modifications to the motherboard. Manufacturers predict PCI Express will replace PCI in the coming years.

PCIe—See PCI Express.

PCIx—See PCI Express.

PCMCIA (Personal Computer Memory Card International Association)—A group of computer manufacturers who developed an interface for connecting any type of device to a portable computer. PCMCIA slots may hold memory, modem, network interface, external hard disk, or CD-ROM cards. PCMCIA-standard cards include PC Card, CardBus, and the newest, ExpressCard.

PD (powered device)—On a network using Power over Ethernet, a node that receives power from power sourcing equipment.

PDA (personal digital assistant)—A handheld computer. PDAs normally use a stylus for user input and often communicate via infrared or another wireless signaling method.

PDU (protocol data unit)—A unit of data at any layer of the OSI Model.

peer-to-peer network—A network in which every computer can communicate directly with every other computer. By default, no computer on a peer-to-peer network has more authority than another. However, each computer can be configured to share only some of its resources and keep other resources inaccessible to other nodes on the network.

Glossary 803

per seat—In the context of applications, a licensing mode that limits access to an application to specific users or workstations. In the context of Microsoft’s Windows Server 2003, a licensing mode that requires a license for every client capable of connecting to the Windows Server 2003 server.

per server—A Windows Server 2003 licensing mode that allows a limited number of clients to access the server simultaneously. (The number is determined by your Windows Server 2003 purchase agreement.) The restriction applies to the number of concurrent connections, rather than specific clients. Per server mode is the most popular choice for installing Windows Server 2003.

per user—A licensing mode that allows a fixed quantity of clients to use one software package simultaneously.

performance management—The ongoing assessment of how well network links, devices, and components keep up with demands on them.

Peripheral Component Interconnect—See PCI. permanent virtual circuit—See PVC.

personal area network—See PAN.

Personal Computer Memory Card International Association—See PCMCIA. personal digital assistant—See PDA.

PGP (Pretty Good Privacy)—A key-based encryption system for e-mail that uses a two-step verification process.

phase—A point or stage in a wave’s progress over time.

physical address—See MAC address.

Physical layer—The lowest, or first, layer of the OSI Model. Protocols in the Physical layer generate and detect voltage so as to transmit and receive signals carrying data over a network medium. These protocols also set the data transmission rate and monitor data error rates, but do not provide error correction.

physical memory—The RAM chips installed on the computer’s system board that provide dedicated memory to that computer.

physical topology—The physical layout of a network. A physical topology depicts a network in broad scope; it does not specify devices, connectivity methods, or addresses on the network. Physical topologies are categorized into three fundamental geometric shapes: bus, ring, and star. These shapes can be mixed to create hybrid topologies.

piconet—A PAN (personal area network) that relies on Bluetooth transmission technology.

pilot network—A small-scale network that stands in for the larger network. A pilot network may be used to evaluate the effects of network changes or additions.

PING (Packet Internet Groper)—A TCP/IP troubleshooting utility that can verify that TCP/IP is installed, bound to the NIC, configured correctly, and communicating with the network. PING uses ICMP to send echo request and echo reply messages that determine the validity of an IP address.

ping—To send an echo request signal from one node on a TCP/IP-based network to another, using the PING utility. See also PING.

804 Glossary

pipe—A_character that enables you to combine existing commands to form new commands. The pipe symbol is the vertical bar (“|”).

pipeline—A series of two or more commands in which the output of prior commands is sent to the input of subsequent commands.

plain old telephone service (POTS)—See PSTN.

plenum—The area above the ceiling tile or below the subfloor in a building.

PoE (Power over Ethernet)—A method of delivering current to devices using Ethernet connection cables.

Point-to-Point Protocol—See PPP.

Point-to-Point Protocol over Ethernet—See PPPoE.

Point-to-Point Tunneling Protocol—See PPTP.

point-to-point—A data transmission that involves one transmitter and one receiver.

polling—A network management application’s regular collection of data from managed devices.

polymorphic virus—A type of virus that changes its characteristics (such as the arrangement of its bytes, size, and internal instructions) every time it is transferred to a new system, making it harder to identify.

pool—A collection of storage objects in NetWare 6.x.

POP (Post Office Protocol)—An Application layer protocol used to retrieve messages from a mail server. When a client retrieves mail via POP, messages previously stored on the mail server are downloaded to the client’s workstation, and then deleted from the mail server.

POP3 (Post Office Protocol, version 3)—The most commonly used form of the Post Office Protocol.

populated segment—A network segment that contains end nodes, such as workstations.

port forwarding—The process of redirecting traffic from its normally assigned port to a different port, either on the client or server. In the case of using SSH, port forwarding can send data exchanges that are normally insecure through encrypted tunnels.

port number—The address on a host where an application makes itself available to incoming data.

Post Office Protocol—See POP.

Post Office Protocol, version 3—See POP3.

POTS—See PSTN.

Power over Ethernet—See PoE. power sourcing equipment—See PSE. powered device—See PD.

PowerPC—The brand of computer central processing unit invented by Apple Computer, IBM, and Motorola, Inc., and used in Apple computers and IBM servers.

PPP (Point-to-Point Protocol)—A communications protocol that enables a workstation to connect to a server using a serial connection. PPP can support multiple Network layer protocols and can use both

Glossary 805

asynchronous and synchronous communications. It performs compression and error correction and requires little configuration on the client workstation.

PPPoE (Point-to-Point Protocol over Ethernet)—PPP running over an Ethernet network.

PPTP (Point-to-Point Tunneling Protocol)—A Layer 2 protocol developed by Microsoft that encapsulates PPP data for transmission over VPN connections. PPTP operates with Windows RRAS access services and can accept connections from multiple different clients. It is simple, but less secure than other modern tunneling protocols.

preamble—The field in an Ethernet frame that signals to the receiving node that data is incoming and indicates when the data flow is about to begin.

predecessor—A task in a project that must be completed before other tasks can begin.

preemptive multitasking—The type of multitasking in which tasks are actually performed one at a time, in very brief succession. In preemptive multitasking, one program uses the processor for a certain period of time, then is suspended to allow another program to use the processor.

Presentation layer—The sixth layer of the OSI Model. Protocols in the Presentation layer translate between the application and the network. Here, data are formatted in a schema that the network can understand, with the format varying according to the type of network used. The Presentation layer also manages data encryption and decryption, such as the scrambling of system passwords.

Pretty Good Privacy—See PGP.

PRI (Primary Rate Interface)—A type of ISDN that uses 23 bearer channels and one 64-Kbps data channel, represented by the notation 23B+D. PRI is less commonly used by individual subscribers than BRI, but it may be used by businesses and other organizations needing more throughput.

principal—In Kerberos terminology, a user or client.

print services—The network service that allows printers to be shared by several users on a network.

printer queue—A logical representation of a networked printer’s functionality. To use a printer, clients must have access to the printer queue.

private branch exchange – See PBX.

private key encryption—A type of key encryption in which the sender and receiver use a key to which only they have access. DES (data encryption standard), which was developed by IBM in the 1970s, is a popular example of a private key encryption technique. Private key encryption is also known as symmetric encryption.

probe—In 802.11 wireless networking, a type of frame issued by a station during active scanning to find nearby access points.

process—A routine of sequential instructions that runs until it has achieved its goal. For example, a spreadsheet program is a process.

project management—The practice of managing staff, budget, timelines, and other resources and variables to complete a specific goal within given bounds.

project plan—The way in which details of a managed project (for example, the timeline and the significant tasks) are organized. Some project plans are created via special project planning software, such as Microsoft Project.

806 Glossary

promiscuous mode—The feature of a network adapter that allows it to pick up all frames that pass over the network—not just those destined for the node served by the card.

proprietary UNIX—Any implementation of UNIX for which the source code is either unavailable or available only by purchasing a licensed copy from The SCO Group (costing as much as millions of dollars). Redistribution of proprietary UNIX versions requires paying royalties to The SCO Group.

protocol—A standard method or format for communication between network devices. Protocols ensure that data are transferred whole, in sequence, and without error from one node on the network to another.

protocol analyzer—A software package or hardware-based tool that can capture and analyze data on a network. Protocol analyzers are more sophisticated than network monitoring tools, as they can typically interpret data up to Layer 7 of the OSI Model.

protocol data unit—See PDU.

proxy—See proxy server.

proxy server—A network host that runs a proxy service. Proxy servers may also be called gateways.

proxy service—A software application on a network host that acts as an intermediary between the external and internal networks, screening all incoming and outgoing traffic and providing one address to the outside world, instead of revealing the addresses of internal LAN devices.

PSE (power sourcing equipment)—On a network using Power over Ethernet, the device that supplies power to end nodes.

PSTN (Public Switched Telephone Network)—The traditional telephone network, from the lines that connect homes and businesses to the network centers that connect different regions of a country. Now, except for the local loop, nearly all of the PSTN uses digital transmission. Its traffic is carried by fiberoptic and copper twisted-pair cable, microwave, and satellite connections.

public key encryption—A form of key encryption in which data is encrypted using two keys: One is a key known only to a user, and the other is a key associated with the user and can be obtained from a public source, such as a public key server. Some examples of public key algorithms include RSA (named after its creators, Rivest, Shamir, and Adleman), Diffie-Hellman, and Elliptic-curve cryptography. Public key encryption is also known as asymmetric encryption.

public key server—A publicly available host (such as an Internet host) that provides free access to a list of users’ public keys (for use in public key encryption).

Public Switched Telephone Network—See PSTN.

punch-down block—A panel of data receptors into which horizontal cabling from the workstations is inserted.

PVC (permanent virtual circuit)—A point-to-point connection over which data may follow any number of different paths, as opposed to a dedicated line that follows a predefined path. X.25, Frame Relay, and some forms of ATM use PVCs.

quality of service (QoS)—The result of standards for delivering data within a certain period of time after their transmission. For example, ATM networks can supply four QoS levels, from a “best effort” attempt for noncritical data to a guaranteed, real-time transmission for time-sensitive data.

Glossary 807

radiation pattern—The relative strength over a three-dimensional area of all the electromagnetic energy an antenna sends or receives.

radiofrequency interference—See RFI.

RADIUS (Remote Authentication Dial-In User Service)—A protocol that runs over UDP and provides centralized network authentication and accounting for multiple users. RADIUS is commonly used with dial-up networking, VPNs, and wireless connections.

RADIUS server—A server that offers centralized authentication services to a network’s access server, VPN server, or wireless access point via the RADIUS protocol.

RAID (Redundant Array of Independent (or Inexpensive) Disks)—A server redundancy measure that uses shared, multiple physical or logical hard disks to ensure data integrity and availability. Some RAID designs also increase storage capacity and improve performance. See also disk mirroring and disk striping.

RAID Level 0—An implementation of RAID in which data is written in 64-KB blocks equally across all disks in the array.

RAID Level 1—An implementation of RAID that provides redundancy through disk mirroring, in which data from one disk is automatically copied to another disk as the information is written.

RAID Level 3—An implementation of RAID that uses disk striping for data and writes parity error correction code on a separate parity disk.

RAID Level 5—The most popular fault-tolerant data storage technique in use today, RAID Level 5 writes data in small blocks across several disks. At the same time, it writes parity error checking information among several disks.

range—The geographical area in which signals issued from an antenna or wireless system can be consistently and accurately received.

RARP (Reverse Address Resolution Protocol)—A core protocol in the TCP/IP suite that belongs in the Network layer of the OSI Model. RARP relies on a RARP table to associate the IP (logical) address of a node with its MAC (physical) address. RARP can be used to supply IP addresses to diskless workstations.

RAS (Remote Access Service)—The dial-up networking software provided with Microsoft Windows 95, 98, NT, and 2000 client operating systems and Windows NT and 2000 network operating systems. RAS requires software installed on both the client and server, a server configured to accept incoming clients, and a client with sufficient privileges (including user name and password) on the server to access its resources. In more recent versions of Windows, RAS has been incorporated into the RRAS (Routing and Remote Access Service).

RC4—An asymmetric key encryption technique that weaves a key with data multiple times as a computer issues the stream of data. RC4 keys can be as long as 2048 bits. In addition to being highly secure, RC4 is fast.

RDN (relative distinguished name)—An attribute of an object that identifies the object separately from its related container(s) and domain. For most objects, the relative distinguished name is the same as its common name (CN) in the distinguished name convention.

808 Glossary

RDP (Remote Desktop Protocol)—An Application layer protocol that uses TCP/IP to transmit graphics and text quickly over a remote client-host connection. RDP also carries session, licensing, and encryption information.

reassembly—The process of reconstructing data units that have been segmented.

reassociation—In the context of wireless networking, the process of a station establishing a connection (or associating) with a different access point.

recordable DVD—An optical storage medium that can hold up to 4.7 GB on one single-layered side. Both sides of the disc can be used, and each side can have up to two layers. Thus, in total, a double-lay- ered, two-sided DVD can store up to 17 GB of data. Recordable DVDs come in several different formats.

redirector—A service that runs on a client workstation and determines whether the client’s request should be handled by the client or the server.

redundancy—The use of more than one identical component, device, or connection for storing, processing, or transporting data. Redundancy is the most common method of achieving fault tolerance.

Redundant Array of Independent (or Inexpensive) Disks—See RAID.

reflection—In the context of wireless, the phenomenon that occurs when an electromagnetic wave encounters an obstacle and bounces back toward its source. A wireless signal will bounce off objects whose dimensions are large compared to the signal’s average wavelength.

regeneration—The process of retransmitting a digital signal. Regeneration, unlike amplification, repeats the pure signal, with none of the noise it has accumulated.

Regional Internet Registry—See RIR.

Registered Ports—TCP/IP ports in the range of 1024 to 49151. These ports are accessible to network users and processes that do not have special administrative privileges. Default assignments of these ports must be registered with IANA.

relative distinguished name—See RDN.

release—The act of terminating a DHCP lease.

remote access—A method for connecting and logging on to a LAN from a workstation that is remote, or not physically connected, to the LAN. Remote access can be accomplished by one of many ways, including dial-up connections, terminal services, remote control, or Web portals.

remote access server—A server that runs communications services that enable remote users to log on to a network. Also known as a communications server or access server.

Remote Access Service—See RAS.

Remote Authentication Dial-In User Service—See RADIUS.

remote control—A remote access method in which the remote user dials into a workstation that is directly attached to a LAN. Software running on both the remote user’s computer and the LAN computer allows the remote user to “take over” the LAN workstation. Only keystrokes, mouse clicks, and screen updates are exchanged between the two computers.

Remote Desktop—An optional feature in Windows XP operating systems that allows a Windows XP computer to be remotely controlled from a client running the Windows 95, 98, Me, NT, XP, 2000, or

Glossary 809

Server 2003 operating system. Remote Desktop is also the program Windows XP clients use to connect with computers using Windows Terminal Server.

Remote Desktop Protocol—See RDP.

Remote Manager—A browser-based tool that enables network administrators to perform server and object management in NetWare 6.5.

remote user—A person working on a computer on a different network or in a different geographical location from the LAN’s server.

removable disk drive—See external disk drive.

Rendezvous—Apple Computer’s implementation of the Zeroconf group of protocols.

repeater—A device used to regenerate a signal.

replication—The process of copying Active Directory data to multiple domain controllers. This ensures redundancy so that in case one of the domain controllers fails, clients can still log on to the network, be authenticated, and access resources.

Request to Send/Clear to Send—See RTS/CTS.

resolver—Any host on the Internet that needs to look up domain name information.

resource record—The element of a DNS database stored on a name server that contains information about TCP/IP host names and their addresses.

resources—The devices, data, and data storage space provided by a computer, whether standalone or shared.

restore—The process of retrieving files from a backup. It is necessary to restore files if the original files are lost or deleted.

Reverse Address Resolution Protocol—See RARP.

RFI (radiofrequency interference)—A kind of interference that may be generated by broadcast signals from radio or TV towers.

RG-6—A type of coaxial cable used for television, satellite, and broadband cable connections.

Rijndael—The algorithm used for AES encryption.

ring topology—A network layout in which each node is connected to the two nearest nodes so that the entire network forms a circle. Data is transmitted unidirectionally around the ring. Each workstation accepts and responds to packets addressed to it, then forwards the other packets to the next workstation in the ring.

ring topology WAN—A type of WAN in which each site is connected to two other sites so that the entire WAN forms a ring pattern.

RIP (Routing Information Protocol)—The oldest routing protocol that is still widely used, RIP does not work in very large network environments in which data may have to travel through more than 15 routers to reach their destination (for example, on the Internet). And, compared to other routing protocols, RIP is slower and less secure.

810 Glossary

RIR (Regional Internet Registry)—A not-for-profit agency that manages the distribution of IP addresses to private and public entities. ARIN is the RIR for North, Central, and South America and sub-Saharan Africa. APNIC is the RIR for Asia and the Pacific region. RIPE is the RIR for Europe and North Africa.

risers—The backbone cabling that provides vertical connections between floors of a building.

RJ-11 (Registered Jack 11)—The standard connector used with unshielded twisted-pair cabling (usually CAT 3 or Level 1) to connect analog telephones.

RJ-45 (Registered Jack 45)—The standard connector used with shielded twisted-pair and unshielded twisted-pair cabling.

root—A highly privileged user ID that has all rights to create, delete, modify, move, read, write, or execute files on a system. This term may also refer to the network administrator.

root domain—In Windows Server 2003 networking, the single domain from which child domains branch out in a domain tree.

root server—A DNS server maintained by ICANN and IANA that is an authority on how to contact the top-level domains, such as those ending with .com, .edu, .net, .us, and so on. ICANN oversees the operation of 13 root servers around the world.

round trip time—See RTT.

routable—Protocols that can span more than one LAN because they carry Network layer and addressing information that can be interpreted by a router.

route—To direct data intelligently between networks based on addressing, patterns of usage, and availability of network segments.

router—A multiport device that operates at Layer 3 of the OSI Model and uses logical addressing information to direct data between networks or segments. Routers can connect dissimilar LANs and WANs running at different transmission speeds and using a variety of Network layer protocols. They determine the best path between nodes based on traffic congestion, available versus unavailable routes, load balancing targets, and other factors.

Routing and Remote Access service (RRAS)—The software included with Windows NT, Windows 2000 Server, and Windows Server 2003 that enables a server to act as a router, firewall, and remote access server. Using RRAS, a server can provide network access to multiple remote clients.

Routing Information Protocol—See RIP.

routing protocols—The means by which routers communicate with each other about network status. Routing protocols determine the best path for data to take between nodes.

routing switch—See Layer 3 switch.

RRAS—See Routing and Remote Access Service.

RSA—An encryption algorithm that creates a key by randomly choosing two large prime numbers and multiplying them together. RSA is named after its creators, Ronald Rivest, Adi Shamir, and Leonard Adleman. RSA was released in 1977, but remains popular today for e-commerce transactions.

Glossary 811

RTS/CTS (Request to Send/Clear to Send)—An exchange in which a wireless station requests the exclusive right to communicate with an access point and the access point confirms that it has granted that request.

RTT (round trip time)—The length of time it takes for a packet to go from sender to receiver, then back from receiver to sender. RTT is usually measured in milliseconds.

runt—A packet that is smaller than the medium’s minimum packet size. For instance, any Ethernet packet that is smaller than 64 bytes is considered a runt.

sag—See brownout.

Samba—An open source software package that provides complete Windows-style fileand printer-shar- ing capabilities.

SAN (storage area network)—A distinct network of multiple storage devices and servers that provides fast, highly available, and highly fault-tolerant access to large quantities of data for a client/server network. A SAN uses a proprietary network transmission method (such as Fibre Channel) rather than a traditional network transmission method such as Ethernet.

satellite return—A type of satellite Internet access service in which a subscriber sends and receives data to and from the Internet over the satellite link. This is a symmetrical technology, in which both upstream and downstream throughputs are advertised to reach 400–500 Kbps; in reality, throughput is often higher.

SC (Subscriber Connector or Standard Connector)—A connector used with single-mode or multimode fiber-optic cable.

scalable—The property of a network that allows you to add nodes or increase its size easily.

scanning—The process a wireless station undergoes to find an access point. See also active scanning and passive scanning.

scattering—The diffusion of a wireless signal that results from hitting an object that has smaller dimensions compared to the signal’s wavelength. Scattering is also related to the roughness of the surface a wireless signal encounters. The rougher the surface, the more likely a signal is to scatter when it hits that surface.

scatternet—A network composed of multiple piconets using Bluetooth transmission technology.

schema—The description of object types, or classes, and their required and optional attributes that are stored in an NOS’s directory.

SCP (Secure CoPy)—A method for copying files securely between hosts. SCP is part of the OpenSSH package, which comes with most modern UNIX-type of operating systems. Third-party SCP applications are available for Windows-based computers.

screening firewall—See packet-filtering firewall.

SDH (Synchronous Digital Hierarchy)—The international equivalent of SONET.

Secure CoPy—See SCP.

Secure Shell—See SSH.